If you want to find sticker printing companies which could do die cut, circle, and other types of stickers. Here are some of my best recommendation:http://www.stickermac.com
They provided the best quality and price out there.
If you are a print broker. You need to have a fast turnaround and most importantly, lowest print price on the market. Here is my list: http://www.eprinttrade.com
For some other alternatives for great printers. Here it is: http://www.bluefinprinting.com